Hydrogen gas is very important for hydrogenation of chemical compounds, in semiconductor fabrication and in ammonia synthesis, to name but a few uses. It is frequently produced by separating carbon monoxide and hydrogen resulting from high-temperature gasification of coal, or from petroleum products. However, this hydrogen is not sufficiently pure for many applications.
High purity hydrogen is needed in the food industry to produce margarines, for example. Pure oxygen is important in life support systems in hospitals, submarines, space vehicles, and so on. Electrolysis methods are generally recognized for providing high purity products, and water electrolysis methods in particularly are useful in yielding hydrogen and oxygen of sufficient purity for such applications.
Methods for the electrolysis of water are known. One representative electrolytic cell configuration for electrolysis of water would comprise an anode (+) and cathode (+) separated by a physical barrier, e.g., porous diaphragm comprised of asbestos, microporous separator of polytetrafluoroethylene (PTFE), and the like. An aqueous electrolyte containing a small amount of ionically conducting acid or base fills the anode and cathode compartments of the cell. With application of a voltage across the electrodes hydrogen gas is formed at the cathode and oxygen is generated at the anode.
Heretofore, methods of electrolyzing water have had several disadvantages. For example, anodes can form oxides which can passivate with some metals. Cathodes can deposit contaminants like metals, organic residues and particulates, thereby coating, passivating or even changing their electrocatalytic behavior. The bubble size of evolved gases too can be such as to blanket the electrodes with an almost insulating film. These effects lead to higher capital and operating costs due to higher cell voltages, as well as losses in current efficiency.
Most processes for electrolyzing water have failed to increase reaction temperatures or generate sufficient heat especially at the electrodes to effectively increase rates of chemical reactions in or at the electrodes, for anode or cathode cleaning, assist in minimizing gas blanketing effects, or enhance the incorporation and storage of hydrogen in cathodes in facilitating the formation of useful metal hydrides, for instance. Because of the above shortcomings, processes for electrolyzing water have not always been conducted under the most economical conditions, for example, at higher current densities.
Accordingly, there is a need for improved methods and apparatus for electrolysis of water which are capable of enhancing the generation of oxygen, hydrogen and heat.